Molecular Regulatory Mechanisms Of Wheat Spike Domestication Traits And Tillering

The domestication gene Q is largely responsible for the widespread cultivation of wheat because it confers multiple domestication traits.However,the underlying molecular mechanisms of how Q regulates these domestication traits remain unclear.In this study,we identify a Q-interacting protein QIP1/Ta LAX1,a b HLH transcription factor,through the yeast two-hybrid assays.We find that Ta LAX1 regulates wheat domestication traits.Overexpression of Ta LAX1 produces phenotypes,reminiscent of the q allele;loss-of-function Talax1 mutations confer compact spikes,largely similar to the Q-overexpression wheat lines.Furthermore,we show that Ta LAX1 directly regulates the transcription of lignin biosynthesis-related gene Ta KNAT7-4D;the two transcription factors Ta LAX1 and Q antagonistically regulate the expression of Ta KNAT7-4D.Consistently,Q and Ta LAX1 disturb each other's activity by interfering with each other's dimer formation.More interestingly,a natural variation(In Del,+/-TATA),which occurs in the promoter of Ta LAX1,is associated with the promoter activity diversity between the D subgenome of bread wheat and its ancestor Aegilops tauschii(DD)accession T093.Together,our study reveals that the transcription factor Ta LAX1 physically interacts with Q to antagonistically regulate wheat domestication traits and a natural variation(In Del,+/-TATA)is associated with the diversification of Ta LAX1 promoter activity.It is well known that spike number,grain number per spike and thousand grain weight have great contribution to the crop yield and the tillers per plant determines the spike number per plant in wheat.The identification and characterization of the regulatory genes associated with wheat tiller number is indispensable for both understanding the genetic basis of phenotypic variation and facilitating the breeding of elite varieties with ideal wheat plant architecture.However,in addition to the wheat “green revolution” gene Reduced height1(Rht1),the main genes that determine wheat plant architecture remain to be identified.Therefore,the cloning of genes controlling wheat plant architecture and elucidating their molecular mechanisms are important to cultivate new high-yielding wheat varieties.In this study,we found that Ta PIL1 acts a repressor of tillering in wheat.Moreover,the transcription factor Ta PIL1 upregulates the transcription of Ta TB1 gene.The transient expression assays showed that Ta PIL1 could activate the transcription of Ta TB1-4A/4B/4D;Ch IP-PCR analyses indicated that Ta PIL1 directly binds to the promoter of Ta TB1-4A.Furthermore,we show that Ta PIL1 physically interacts with Ta SPL3/17.Taken together,we conclude that the Ta PIL1 transcription factors play an important role in controlling tillering in wheat.